Row level lock code for the archive storage engine.

sql/examples/ha_archive.cc

@@ -42,7 +42,18 @@
   handle bulk inserts as well (that is if someone was trying to read at
   the same time since we would want to flush).
 
-  No attempts at durability are made. You can corrupt your data.
+  A "meta" file is kept. All this file does is contain information on
+  the number of rows. 
+
+  No attempts at durability are made. You can corrupt your data. A repair
+  method was added to repair the meta file that stores row information,
+  but if your data file gets corrupted I haven't solved that. I could
+  create a repair that would solve this, but do you want to take a 
+  chance of loosing your data?
+
+  Locks are row level, and you will get a consistant read. Transactions
+  will be added later (they are not that hard to add at this
+  stage). 
 
   For performance as far as table scans go it is quite fast. I don't have
   good numbers but locally it has out performed both Innodb and MyISAM. For
@@ -71,14 +82,35 @@
    Add truncate table command.
    Implement versioning, should be easy.
    Allow for errors, find a way to mark bad rows.
-   See if during an optimize you can make the table smaller.
    Talk to the gzip guys, come up with a writable format so that updates are doable
      without switching to a block method.
    Add optional feature so that rows can be flushed at interval (which will cause less
-   compression but may speed up ordered searches).
+     compression but may speed up ordered searches).
+   Checkpoint the meta file to allow for faster rebuilds.
+   Dirty open (right now the meta file is repaired if a crash occured).
+   Transactions.
+   Option to allow for dirty reads, this would lower the sync calls, which would make
+     inserts a lot faster, but would mean highly arbitrary reads.
 
     -Brian
 */
+/*
+  Notes on file formats.
+  The Meta file is layed out as:
+  check - Just an int of 254 to make sure that the the file we are opening was
+          never corrupted.
+  version - The current version of the file format.
+  rows - This is an unsigned long long which is the number of rows in the data
+         file.
+  check point - Reserved for future use
+  dirty - Status of the file, whether or not its values are the latest. This flag
+          is what causes a repair to occur
+
+  The data file:
+  check - Just an int of 254 to make sure that the the file we are opening was
+          never corrupted.
+  version - The current version of the file format.
+  data - The data is stored in a "row +blobs" format.
 
 /* Variables for archive share methods */
 pthread_mutex_t archive_mutex;
@@ -86,8 +118,11 @@ static HASH archive_open_tables;
 static int archive_init= 0;
 
 /* The file extension */
-#define ARZ ".ARZ"
-#define ARN ".ARN"
+#define ARZ ".ARZ"          // The data file
+#define ARN ".ARN"          // Files used during an optimize call
+#define ARM ".ARM"          // Meta file
+#define META_BUFFER_SIZE 24 // Size of the data used in the meta file
+#define CHECK_HEADER 254    // The number we use to determine corruption
 
 /*
   Used for hash table that tracks open tables.
@@ -99,14 +134,132 @@ static byte* archive_get_key(ARCHIVE_SHARE *share,uint *length,
   return (byte*) share->table_name;
 }
 
+/*
+  This method reads the header of a datafile and returns whether or not it was successful.
+*/
+int ha_archive::read_data_header(gzFile file_to_read)
+{
+  int check; // We use this to check the header
+
+  DBUG_ENTER("ha_archive::read_data_header");
+
+  if (gzrewind(file_to_read) == -1)
+    DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
+
+  if (gzread(file_to_read, &check, sizeof(int)) != sizeof(int))
+    DBUG_RETURN(errno ? errno : -1);
+  if (check != CHECK_HEADER)
+    DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
+  if (gzread(file_to_read, &version, sizeof(version)) != sizeof(version))
+    DBUG_RETURN(errno ? errno : -1);
+
+  DBUG_RETURN(0);
+}
 
 /*
-  Example of simple lock controls.
-  See ha_example.cc for a description.
+  This method writes out the header of a datafile and returns whether or not it was successful.
+*/
+int ha_archive::write_data_header(gzFile file_to_write)
+{
+  int check= CHECK_HEADER;
+  DBUG_ENTER("ha_archive::write_data_header");
+
+  if (gzwrite(file_to_write, &check, sizeof(int)) != sizeof(int))
+    goto error;
+  if (gzwrite(file_to_write, &version, sizeof(int)) != sizeof(version))
+    goto error;
+
+  DBUG_RETURN(0);
+error:
+  DBUG_RETURN(errno);
+}
+
+/*
+  This method reads the header of a meta file and returns whether or not it was successful.
+  *rows will contain the current number of rows in the data file upon success.
+*/
+int ha_archive::read_meta_file(File meta_file, ulonglong *rows)
+{
+  size_t size= sizeof(ulonglong) + sizeof(version) + sizeof(bool); // calculate
+  byte meta_buffer[META_BUFFER_SIZE];
+  bool dirty;
+  int check;
+  ulonglong check_point;
+
+  DBUG_ENTER("ha_archive::read_meta_file");
+
+  /* 
+    Format of the meta file is:
+    version
+    number of rows
+    byte showing if the file was stored
+  */
+  VOID(my_seek(meta_file, 0, MY_SEEK_SET, MYF(0)));
+  if (my_read(meta_file, meta_buffer, size, MYF(MY_WME | MY_NABP)))
+    DBUG_RETURN(-1);
+  
+  /*
+    Parse out the meta data, we ignore version at the moment
+  */
+  memcpy(&check, meta_buffer + sizeof(int), sizeof(int));
+  longlongstore(rows, meta_buffer + sizeof(version) + sizeof(int));
+  longlongstore(&check_point, meta_buffer + sizeof(version) + sizeof(int) +
+                sizeof(ulonglong));
+  memcpy(&dirty, meta_buffer+sizeof(ulonglong) + sizeof(version) + 
+         sizeof(ulonglong) + sizeof(int), sizeof(bool));
+
+  if (dirty == TRUE)
+    DBUG_RETURN(-1);
+
+  my_sync(meta_file, MYF(MY_WME));
+
+  DBUG_RETURN(0);
+}
+
+/*
+  This method writes out the header of a meta file and returns whether or not it was successful.
+  By setting dirty you say whether or not the file represents the actual state of the data file.
+  Upon ::open() we set to dirty, and upon ::close() we set to clean. If we determine during
+  a read that the file was dirty we will force a rebuild of this file.
+*/
+int ha_archive::write_meta_file(File meta_file, ulonglong rows, bool dirty)
+{
+  char meta_buffer[META_BUFFER_SIZE];
+  ulonglong check_port= 0;
+  size_t size= sizeof(ulonglong) + sizeof(version) + sizeof(bool) +
+    sizeof(ulonglong); // calculate length of data
+  DBUG_ENTER("ha_archive::write_meta_file");
+
+  /* 
+    Format of the meta file is:
+    version
+    number of rows
+    byte showing if the file was stored
+  */
+  version= ARCHIVE_VERSION;
+  memcpy(meta_buffer, &version, sizeof(version));
+  longlongstore(meta_buffer + sizeof(version), rows); // Position past version
+  longlongstore(meta_buffer + sizeof(version) + sizeof(ulonglong), check_port);
+  memcpy(meta_buffer+sizeof(ulonglong) + sizeof(version) + + sizeof(ulonglong), &dirty, sizeof(bool));
+
+  VOID(my_seek(meta_file, 0, MY_SEEK_SET, MYF(0)));
+  if (my_write(meta_file, meta_buffer, size, MYF(MY_WME | MY_NABP)))
+    DBUG_RETURN(-1);
+  
+  my_sync(meta_file, MYF(MY_WME));
+
+  DBUG_RETURN(0);
+}
+
+
+/*
+  We create the shared memory space that we will use for the open table. 
+  See ha_example.cc for a longer description.
 */
-static ARCHIVE_SHARE *get_share(const char *table_name, TABLE *table)
+ARCHIVE_SHARE *ha_archive::get_share(const char *table_name, TABLE *table)
 {
   ARCHIVE_SHARE *share;
+  char meta_file_name[FN_REFLEN];
   uint length;
   char *tmp_name;
 
@@ -143,33 +296,62 @@ static ARCHIVE_SHARE *get_share(const char *table_name, TABLE *table)
       return NULL;
     }
 
-    share->use_count=0;
-    share->table_name_length=length;
-    share->table_name=tmp_name;
+    share->use_count= 0;
+    share->table_name_length= length;
+    share->table_name= tmp_name;
     fn_format(share->data_file_name,table_name,"",ARZ,MY_REPLACE_EXT|MY_UNPACK_FILENAME);
+    fn_format(meta_file_name,table_name,"",ARM,MY_REPLACE_EXT|MY_UNPACK_FILENAME);
     strmov(share->table_name,table_name);
+    /*
+      We will use this lock for rows.
+    */
+    VOID(pthread_mutex_init(&share->mutex,MY_MUTEX_INIT_FAST));
+    if ((share->meta_file= my_open(meta_file_name, O_RDWR, MYF(0))) == -1)
+      goto error;
+    
+    if (read_meta_file(share->meta_file, &share->rows_recorded))
+    {
+      /*
+        The problem here is that for some reason, probably a crash, the meta
+        file has been corrupted. So what do we do? Well we try to rebuild it
+        ourself. Once that happens, we reread it, but if that fails we just
+        call it quits and return an error.
+      */
+      if (rebuild_meta_file(share->table_name, share->meta_file))
+        goto error;
+      if (read_meta_file(share->meta_file, &share->rows_recorded))
+        goto error;
+    }
+    /*
+      After we read, we set the file to dirty. When we close, we will do the 
+      opposite.
+    */
+    (void)write_meta_file(share->meta_file, share->rows_recorded, TRUE);
     /* 
       It is expensive to open and close the data files and since you can't have
       a gzip file that can be both read and written we keep a writer open
       that is shared amoung all open tables.
     */
     if ((share->archive_write= gzopen(share->data_file_name, "ab")) == NULL)
-      goto error;
+      goto error2;
     if (my_hash_insert(&archive_open_tables, (byte*) share))
-      goto error;
+      goto error2;
     thr_lock_init(&share->lock);
     if (pthread_mutex_init(&share->mutex,MY_MUTEX_INIT_FAST))
-      goto error2;
+      goto error3;
   }
   share->use_count++;
   pthread_mutex_unlock(&archive_mutex);
 
   return share;
 
-error2:
+error3:
+  VOID(pthread_mutex_destroy(&share->mutex));
   thr_lock_delete(&share->lock);
   /* We close, but ignore errors since we already have errors */
   (void)gzclose(share->archive_write);
+error2:
+  my_close(share->meta_file,MYF(0));
 error:
   pthread_mutex_unlock(&archive_mutex);
   my_free((gptr) share, MYF(0));
@@ -179,10 +361,10 @@ error:
 
 
 /* 
-  Free lock controls.
+  Free the share.
   See ha_example.cc for a description.
 */
-static int free_share(ARCHIVE_SHARE *share)
+int ha_archive::free_share(ARCHIVE_SHARE *share)
 {
   int rc= 0;
   pthread_mutex_lock(&archive_mutex);
@@ -190,7 +372,8 @@ static int free_share(ARCHIVE_SHARE *share)
   {
     hash_delete(&archive_open_tables, (byte*) share);
     thr_lock_delete(&share->lock);
-    pthread_mutex_destroy(&share->mutex);
+    VOID(pthread_mutex_destroy(&share->mutex));
+    (void)write_meta_file(share->meta_file, share->rows_recorded, FALSE);
     if (gzclose(share->archive_write) == Z_ERRNO)
       rc= 1;
     my_free((gptr) share, MYF(0));
@@ -205,7 +388,7 @@ static int free_share(ARCHIVE_SHARE *share)
   We just implement one additional file extension.
 */
 const char **ha_archive::bas_ext() const
-{ static const char *ext[]= { ARZ, ARN, NullS }; return ext; }
+{ static const char *ext[]= { ARZ, ARN, ARM, NullS }; return ext; }
 
 
 /* 
@@ -213,7 +396,6 @@ const char **ha_archive::bas_ext() const
   Create/get our shared structure.
   Init out lock.
   We open the file we will read from.
-  Set the size of ref_length.
 */
 int ha_archive::open(const char *name, int mode, uint test_if_locked)
 {
@@ -284,36 +466,58 @@ int ha_archive::close(void)
 int ha_archive::create(const char *name, TABLE *table_arg,
                        HA_CREATE_INFO *create_info)
 {
-  File create_file;
+  File create_file;  // We use to create the datafile and the metafile
   char name_buff[FN_REFLEN];
   size_t written;
   int error;
   DBUG_ENTER("ha_archive::create");
 
+  /*
+    Right now version for the meta file and the data file is the same.
+  */
+  version= ARCHIVE_VERSION;
+
+  if ((create_file= my_create(fn_format(name_buff,name,"",ARM,
+                                        MY_REPLACE_EXT|MY_UNPACK_FILENAME),0,
+                              O_RDWR | O_TRUNC,MYF(MY_WME))) < 0)
+  {
+    error= my_errno;
+    goto error;
+  }
+  write_meta_file(create_file, 0, FALSE);
+  my_close(create_file,MYF(0));
+
+  /* 
+    We reuse name_buff since it is available.
+  */
   if ((create_file= my_create(fn_format(name_buff,name,"",ARZ,
                                         MY_REPLACE_EXT|MY_UNPACK_FILENAME),0,
                               O_RDWR | O_TRUNC,MYF(MY_WME))) < 0)
   {
     error= my_errno;
-    goto err;
+    goto error;
   }
   if ((archive= gzdopen(create_file, "ab")) == NULL)
   {
     error= errno;
     delete_table(name);
-    goto err;
+    goto error;
   }
-  version= ARCHIVE_VERSION;
-  written= gzwrite(archive, &version, sizeof(version));
-  if (gzclose(archive) || written != sizeof(version))
+  if (write_data_header(archive))
   {
-    error= errno;
-    delete_table(name);
-    goto err;
+    gzclose(archive);
+    goto error2;
   }
+
+  if (gzclose(archive))
+    goto error2;
+
   DBUG_RETURN(0);
 
-err:
+error2:
+    error= errno;
+    delete_table(name);
+error:
   /* Return error number, if we got one */
   DBUG_RETURN(error ? error : -1);
 }
@@ -330,30 +534,41 @@ err:
 */
 int ha_archive::write_row(byte * buf)
 {
-  char *pos;
   z_off_t written;
   DBUG_ENTER("ha_archive::write_row");
 
   statistic_increment(ha_write_count,&LOCK_status);
   if (table->timestamp_default_now)
     update_timestamp(buf+table->timestamp_default_now-1);
+  pthread_mutex_lock(&share->mutex);
   written= gzwrite(share->archive_write, buf, table->reclength);
   share->dirty= TRUE;
   if (written != table->reclength)
-    DBUG_RETURN(errno ? errno : -1);
-
+    goto error;
+  /*
+    We should probably mark the table as damagaged if the record is written
+    but the blob fails.
+  */
   for (Field_blob **field=table->blob_field ; *field ; field++)
   {
     char *ptr;
     uint32 size= (*field)->get_length();
 
-    (*field)->get_ptr(&ptr);
-    written= gzwrite(share->archive_write, ptr, (unsigned)size);
-    if (written != size)
-      DBUG_RETURN(errno ? errno : -1);
+    if (size)
+    {
+      (*field)->get_ptr(&ptr);
+      written= gzwrite(share->archive_write, ptr, (unsigned)size);
+      if (written != size)
+        goto error;
+    }
   }
+  share->rows_recorded++;
+  pthread_mutex_unlock(&share->mutex);
 
   DBUG_RETURN(0);
+error:
+  pthread_mutex_unlock(&share->mutex);
+  DBUG_RETURN(errno ? errno : -1);
 }
 
 
@@ -369,37 +584,28 @@ int ha_archive::rnd_init(bool scan)
   int read; // gzread() returns int, and we use this to check the header
 
   /* We rewind the file so that we can read from the beginning if scan */
-  if(scan)
+  if (scan)
   {
+    scan_rows= share->rows_recorded;
     records= 0;
-    if (gzrewind(archive))
-      DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
-  }
 
-  /* 
-    If dirty, we lock, and then reset/flush the data.
-    I found that just calling gzflush() doesn't always work.
-  */
-  if (share->dirty == TRUE)
-  {
-    pthread_mutex_lock(&share->mutex);
+    /* 
+      If dirty, we lock, and then reset/flush the data.
+      I found that just calling gzflush() doesn't always work.
+    */
     if (share->dirty == TRUE)
     {
-      gzflush(share->archive_write, Z_SYNC_FLUSH);
-      share->dirty= FALSE;
+      pthread_mutex_lock(&share->mutex);
+      if (share->dirty == TRUE)
+      {
+        gzflush(share->archive_write, Z_SYNC_FLUSH);
+        share->dirty= FALSE;
+      }
+      pthread_mutex_unlock(&share->mutex);
     }
-    pthread_mutex_unlock(&share->mutex);
-  }
-  
-  /* 
-    At the moment we just check the size of version to make sure the header is 
-    intact.
-  */
-  if (scan)
-  {
-    read= gzread(archive, &version, sizeof(version));
-    if (read != sizeof(version))
-      DBUG_RETURN(errno ? errno : -1);
+
+    if (read_data_header(archive))
+      DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
   }
 
   DBUG_RETURN(0);
@@ -410,14 +616,19 @@ int ha_archive::rnd_init(bool scan)
   This is the method that is used to read a row. It assumes that the row is 
   positioned where you want it.
 */
-int ha_archive::get_row(byte *buf)
+int ha_archive::get_row(gzFile file_to_read, byte *buf)
 {
   int read; // Bytes read, gzread() returns int
   char *last;
   size_t total_blob_length= 0;
+  Field_blob **field;
   DBUG_ENTER("ha_archive::get_row");
 
-  read= gzread(archive, buf, table->reclength);
+  read= gzread(file_to_read, buf, table->reclength);
+  DBUG_PRINT("ha_archive::get_row", ("Read %d bytes", read));
+
+  if (read == Z_STREAM_ERROR)
+    DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
 
   /* If we read nothing we are at the end of the file */
   if (read == 0)
@@ -428,7 +639,7 @@ int ha_archive::get_row(byte *buf)
     DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
 
   /* Calculate blob length, we use this for our buffer */
-  for (Field_blob **field=table->blob_field; *field ; field++)
+  for (field=table->blob_field; *field ; field++)
     total_blob_length += (*field)->get_length();
 
   /* Adjust our row buffer if we need be */
@@ -436,14 +647,17 @@ int ha_archive::get_row(byte *buf)
   last= (char *)buffer.ptr();
 
   /* Loop through our blobs and read them */
-  for (Field_blob **field=table->blob_field; *field ; field++)
+  for (field=table->blob_field; *field ; field++)
   {
     size_t size= (*field)->get_length();
-    read= gzread(archive, last, size);
-    if ((size_t) read != size)
-      DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
-    (*field)->set_ptr(size, last);
-    last += size;
+    if (size)
+    {
+      read= gzread(file_to_read, last, size);
+      if ((size_t) read != size)
+        DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
+      (*field)->set_ptr(size, last);
+      last += size;
+    }
   }
   DBUG_RETURN(0);
 }
@@ -459,9 +673,15 @@ int ha_archive::rnd_next(byte *buf)
   int rc;
   DBUG_ENTER("ha_archive::rnd_next");
 
+  if (!scan_rows)
+    DBUG_RETURN(HA_ERR_END_OF_FILE);
+  scan_rows--;
+
   statistic_increment(ha_read_rnd_next_count,&LOCK_status);
   current_position= gztell(archive);
-  rc= get_row(buf);
+  rc= get_row(archive, buf);
+
+
   if (rc != HA_ERR_END_OF_FILE)
     records++;
 
@@ -474,6 +694,7 @@ int ha_archive::rnd_next(byte *buf)
   each call to ha_archive::rnd_next() if an ordering of the rows is
   needed.
 */
+
 void ha_archive::position(const byte *record)
 {
   DBUG_ENTER("ha_archive::position");
@@ -496,13 +717,70 @@ int ha_archive::rnd_pos(byte * buf, byte *pos)
   current_position= ha_get_ptr(pos, ref_length);
   z_off_t seek= gzseek(archive, current_position, SEEK_SET);
 
-  DBUG_RETURN(get_row(buf));
+  DBUG_RETURN(get_row(archive, buf));
+}
+
+/*
+  This method rebuilds the meta file. It does this by walking the datafile and 
+  rewriting the meta file.
+*/
+int ha_archive::rebuild_meta_file(char *table_name, File meta_file)
+{
+  int rc;
+  byte *buf; 
+  ulonglong rows_recorded= 0;
+  gzFile rebuild_file;            /* Archive file we are working with */
+  char data_file_name[FN_REFLEN];
+  DBUG_ENTER("ha_archive::rebuild_meta_file");
+
+  /*
+    Open up the meta file to recreate it.
+  */
+  fn_format(data_file_name, table_name, "", ARZ,
+            MY_REPLACE_EXT|MY_UNPACK_FILENAME);
+  if ((rebuild_file= gzopen(data_file_name, "rb")) == NULL)
+    DBUG_RETURN(errno ? errno : -1);
+
+  if (rc= read_data_header(rebuild_file))
+    goto error;
+
+  /*
+    We malloc up the buffer we will use for counting the rows. 
+    I know, this malloc'ing memory but this should be a very 
+    rare event.
+  */
+  if (!(buf= (byte*) my_malloc(table->rec_buff_length > sizeof(ulonglong) +1 ? 
+                               table->rec_buff_length : sizeof(ulonglong) +1 ,
+                               MYF(MY_WME))))
+  {
+    rc= HA_ERR_CRASHED_ON_USAGE;
+    goto error;
+  }
+
+  while (!(rc= get_row(rebuild_file, buf)))
+    rows_recorded++;
+
+  /* 
+    Only if we reach the end of the file do we assume we can rewrite.
+    At this point we reset rc to a non-message state.
+  */
+  if (rc == HA_ERR_END_OF_FILE)
+  {
+    (void)write_meta_file(meta_file, rows_recorded, FALSE);
+    rc= 0;
+  }
+
+  my_free((gptr) buf, MYF(0));
+error:
+  gzclose(rebuild_file);
+
+  DBUG_RETURN(rc);
 }
 
 /*
   The table can become fragmented if data was inserted, read, and then
   inserted again. What we do is open up the file and recompress it completely. 
-  */
+*/
 int ha_archive::optimize(THD* thd, HA_CHECK_OPT* check_opt)
 {
   DBUG_ENTER("ha_archive::optimize");
@@ -512,7 +790,8 @@ int ha_archive::optimize(THD* thd, HA_CHECK_OPT* check_opt)
   char writer_filename[FN_REFLEN];
 
   /* Lets create a file to contain the new data */
-  fn_format(writer_filename,share->table_name,"",ARN, MY_REPLACE_EXT|MY_UNPACK_FILENAME);
+  fn_format(writer_filename, share->table_name, "", ARN, 
+            MY_REPLACE_EXT|MY_UNPACK_FILENAME);
 
   /* Closing will cause all data waiting to be flushed, to be flushed */
   gzclose(share->archive_write);
@@ -547,6 +826,59 @@ int ha_archive::optimize(THD* thd, HA_CHECK_OPT* check_opt)
   DBUG_RETURN(0); 
 }
 
+
+/*
+  No transactions yet, so this is pretty dull.
+*/
+int ha_archive::external_lock(THD *thd, int lock_type)
+{
+  DBUG_ENTER("ha_archive::external_lock");
+  DBUG_RETURN(0);
+}
+
+/* 
+  Below is an example of how to setup row level locking.
+*/
+THR_LOCK_DATA **ha_archive::store_lock(THD *thd,
+                                       THR_LOCK_DATA **to,
+                                       enum thr_lock_type lock_type)
+{
+  if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK) {
+    /* 
+      Here is where we get into the guts of a row level lock.
+      If TL_UNLOCK is set 
+      If we are not doing a LOCK TABLE or DISCARD/IMPORT
+      TABLESPACE, then allow multiple writers 
+    */
+
+    if ((lock_type >= TL_WRITE_CONCURRENT_INSERT &&
+         lock_type <= TL_WRITE) && !thd->in_lock_tables
+        && !thd->tablespace_op) {
+
+      lock_type = TL_WRITE_ALLOW_WRITE;
+    }
+
+    /* 
+      In queries of type INSERT INTO t1 SELECT ... FROM t2 ...
+      MySQL would use the lock TL_READ_NO_INSERT on t2, and that
+      would conflict with TL_WRITE_ALLOW_WRITE, blocking all inserts
+      to t2. Convert the lock to a normal read lock to allow
+      concurrent inserts to t2. 
+    */
+
+    if (lock_type == TL_READ_NO_INSERT && !thd->in_lock_tables) {
+      lock_type = TL_READ;
+    }
+
+    lock.type=lock_type;
+  }
+
+  *to++= &lock;
+
+  return to;
+}
+
+
 /******************************************************************************
 
   Everything below here is default, please look at ha_example.cc for 
@@ -616,8 +948,8 @@ void ha_archive::info(uint flag)
   DBUG_ENTER("ha_archive::info");
 
   /* This is a lie, but you don't want the optimizer to see zero or 1 */
-  if (records < 2) 
-    records= 2;
+  records= share->rows_recorded;
+  deleted= 0;
 
   DBUG_VOID_RETURN;
 }
@@ -634,23 +966,6 @@ int ha_archive::reset(void)
   DBUG_RETURN(0);
 }
 
-
-int ha_archive::external_lock(THD *thd, int lock_type)
-{
-  DBUG_ENTER("ha_archive::external_lock");
-  DBUG_RETURN(0);
-}
-
-THR_LOCK_DATA **ha_archive::store_lock(THD *thd,
-                                       THR_LOCK_DATA **to,
-                                       enum thr_lock_type lock_type)
-{
-  if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK)
-    lock.type=lock_type;
-  *to++= &lock;
-  return to;
-}
-
 ha_rows ha_archive::records_in_range(uint inx, key_range *min_key,
                                      key_range *max_key)
 {

sql/examples/ha_archive.h

@@ -32,8 +32,10 @@ typedef struct st_archive_share {
   uint table_name_length,use_count;
   pthread_mutex_t mutex;
   THR_LOCK lock;
+  File meta_file;                   /* Meta file we use */
   gzFile archive_write;             /* Archive file we are working with */
   bool dirty;                       /* Flag for if a flush should occur */
+  ulonglong rows_recorded;          /* Number of rows in tables */
 } ARCHIVE_SHARE;
 
 /*
@@ -50,7 +52,8 @@ class ha_archive: public handler
   z_off_t current_position;  /* The position of the row we just read */
   byte byte_buffer[IO_SIZE]; /* Initial buffer for our string */
   String buffer;             /* Buffer used for blob storage */
-  unsigned int version;      /* Used for recording version */
+  uint version;              /* Used for recording version */
+  ulonglong scan_rows;       /* Number of rows left in scan */
 
 public:
   ha_archive(TABLE *table): handler(table)
@@ -104,7 +107,14 @@ public:
   int rnd_init(bool scan=1);
   int rnd_next(byte *buf);
   int rnd_pos(byte * buf, byte *pos);
-  int get_row(byte *buf);
+  int get_row(gzFile file_to_read, byte *buf);
+  int read_meta_file(File meta_file, ulonglong *rows);
+  int write_meta_file(File meta_file, ulonglong rows, bool dirty);
+  ARCHIVE_SHARE *get_share(const char *table_name, TABLE *table);
+  int free_share(ARCHIVE_SHARE *share);
+  int rebuild_meta_file(char *table_name, File meta_file);
+  int read_data_header(gzFile file_to_read);
+  int write_data_header(gzFile file_to_write);
   void position(const byte *record);
   void info(uint);
   int extra(enum ha_extra_function operation);